Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752609AbbKIJJV (ORCPT ); Mon, 9 Nov 2015 04:09:21 -0500 Received: from aserp1040.oracle.com ([141.146.126.69]:28086 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751294AbbKIJJS (ORCPT ); Mon, 9 Nov 2015 04:09:18 -0500 Reply-To: zhenzhong.duan@oracle.com Subject: Re: Question with maxcpus= parameter. References: <563C3980.8060405@oracle.com> <20151106161459.GB4538@char.us.oracle.com> <56403368.60603@oracle.com> To: Yinghai Lu Cc: Konrad Rzeszutek Wilk , Rusty Russell , Ashok Raj , LKML , Feng Jin From: Zhenzhong Duan Organization: Oracle Message-ID: <564062CE.90106@oracle.com> Date: Mon, 9 Nov 2015 17:09:34 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit X-Source-IP: aserv0021.oracle.com [141.146.126.233] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4901 Lines: 118 在 2015/11/9 14:12, Yinghai Lu 写道: > On Sun, Nov 8, 2015 at 9:47 PM, Zhenzhong Duan > wrote: >> Tried nr_cpus=4, works. >> > nr_cpus and maxcpus are different. > > maxcpus=4 means kernel will only bring up 4 cpus, but other cpus still > can be brought up online. > if there are more cpu are there according acpi MADT. > > nr_cpus=4 that means 4 is hard limit, just like you compiled kernel > with CONFIG_NR_CPUS=4. I know that, what confused me is uek2(2.6.39-400.249.4.el6uek.x86_64) works with maxcpus=, but uek3(3.8.13-44.1.1.el6uek.x86_64) not when I don't comment out the script. I have ever suspected uek2 send CPU ADD event for only 4 cpus. dyndbg="file kobject_uevent.c +p" is used when debug, vimdiff with both dmesg: uek2 | uek3 ...... PCI: Using configuration type 1 for base access | PCI: Using configuration type 1 for base access kobject: 'node0' (ffffffff81d6c9d0): kobject_uevent_env | kobject: 'node0' (ffff883f25984410): kobject_uevent_env kobject: 'cpu0' (ffff88407ec0b2f8): kobject_uevent_env | kobject: 'cpu0' (ffff883f7ec0c3d8): kobject_uevent_env kobject: 'cpu1' (ffff88407ec2b2f8): kobject_uevent_env | kobject: 'cpu1' (ffff883f7ec2c3d8): kobject_uevent_env ...... kobject: 'cpu70' (ffff88407f4cb2f8): kobject_uevent_env | kobject: 'cpu70' (ffff883f7f4cc3d8): kobject_uevent_env kobject: 'cpu71' (ffff88407f4eb2f8): kobject_uevent_env | kobject: 'cpu71' (ffff883f7f4ec3d8): kobject_uevent_env ...... dracut: dracut-004-356.0.1.el6 | dracut: dracut-004-356.0.1.el6 dracut: rd_NO_LUKS: removing cryptoluks activation | dracut: rd_NO_LUKS: removing cryptoluks activation kobject: 'dm_mod' (ffffffffa000e290): kobject_uevent_env | kobject: 'dm_mod' (ffffffffa000f3b0): kobject_uevent_env device-mapper: uevent: version 1.0.3 | device-mapper: uevent: version 1.0.3 udev: starting version 147 | udev: starting version 147 ...... kobject: 'cpu0' (ffff883f0076dc10): kobject_uevent_env | kobject: 'cpu0' (ffff883f7ec0c3d8): kobject_uevent_env kobject: 'cpu1' (ffff883f0076d810): kobject_uevent_env | kobject: 'cpu1' (ffff883f7ec2c3d8): kobject_uevent_env kobject: 'cpu2' (ffff883f0076d410): kobject_uevent_env | kobject: 'cpu10' (ffff883f7ed4c3d8): kobject_uevent_env kobject: 'cpu3' (ffff883f0076d010): kobject_uevent_env | kobject: 'cpu11' (ffff883f7ed6c3d8): kobject_uevent_env kobject: 'id' (ffff883f05716c10): kobject_uevent_env | kobject: 'cpu12' (ffff883f7ed8c3d8): kobject_uevent_env kobject: 'fbcon' (ffff883f05779c10): kobject_uevent_env | kobject: 'cpu13' (ffff883f7f42c3d8): kobject_uevent_env ...... | ...... (total 72 cpus) dracut: | dracut: dracut: Switching root | dracut: Switching root udev: starting version 147 | udev: starting version 147 kobject: 'cpu0' (ffff883f0076dc10): kobject_uevent_env | kobject: 'cpu0' (ffff883f7ec0c3d8): kobject_uevent_env kobject: 'cpu1' (ffff883f0076d810): kobject_uevent_env | kobject: 'cpu1' (ffff883f7ec2c3d8): kobject_uevent_env kobject: 'cpu2' (ffff883f0076d410): kobject_uevent_env | kobject: 'cpu10' (ffff883f7ed4c3d8): kobject_uevent_env kobject: 'cpu3' (ffff883f0076d010): kobject_uevent_env | kobject: 'cpu11' (ffff883f7ed6c3d8): kobject_uevent_env kobject: 'id' (ffff883f05716c10): kobject_uevent_env | kobject: 'cpu12' (ffff883f7ed8c3d8): kobject_uevent_env kobject: 'fbcon' (ffff883f05779c10): kobject_uevent_env | kobject: 'cpu13' (ffff883f7f42c3d8): kobject_uevent_env ...... | ...... (total 72 cpus) I looked at the path to send event at bootup, it's almost same, the dmesg confirmed this. uek2 topology_init->arch_register_cpu->register_cpu->sysdev_register->kobject_uevent(&dev->kobj, KOBJ_ADD); uek3 topology_init->arch_register_cpu->register_cpu->device_register->kobject_uevent(&dev->kobj, KOBJ_ADD); But I don't find who send event again after udev start with different cpu count. thanks zduan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/